1. Field of the Invention
The present invention relates to a device for detecting an accurate binary signal from a reproduction output having level variations in a disk apparatus for recording/reproducing data in/from, e.g., an optical disk.
2. Description of the Related Art
As is well known, various types of disk apparatuses for recording data in an optical disk or reading data recorded in the optical disk by using a laser beam emitted from, e.g., a semiconductor laser have been developed.
In the above-mentioned optical disk apparatuses, in order to standardize optical disks, a characteristic data record area is arranged outside a record area (i.e., a region in an inner circumferential portion where no guide grooves and servo bytes are present) of each optical disk. As characteristic data to be recorded in this area, mode data (corresponding to specifications) called a control track is considered. Such control tracks as bar codes are to be commonly recorded in optical disks available from any manufacturers.
Data such as a reflectivity, writing/reading laser power, the number of sectors per track (360.degree. ) of an optical disk are to be recorded in this control track to determine read and write modes (specifications).
In a conventional optical disk apparatus, although methods of accurately reading control tracks have been studied, no study has been made on methods of accurately reading control tracks in a region having no guide grooves and servo bytes in consideration of eccentricity.
The conventional apparatus, therefore, has the following drawback. If eccentricity of an optical disk is large, a control track (characteristic data) recorded in the characteristic data record area having no guide grooves and servo bytes cannot be accurately read.